Conventionally, in a wind power generator, when a nacelle mounted on the top of a tower, a rotor head, a wind-turbine rotor blade, or another large component, such as a gear box, breaks or is damaged and is to be replaced, a large crane is used.
Or, when constructing a wind power generator in a place like a mountainous area, where securing flat land is difficult, wind-turbine rotor blades have to be attached one by one to the rotor head. That is, because the wind-turbine rotor blades have to be attached to the rotor head on flat land, when securing flat land is difficult, the wind-turbine rotor blades have to be attached one by one to the rotor head mounted on the top of the tower (for example, refer to Patent Document 1).    Patent Document 1: Japanese Translation of PCT International Application, Publication No. 2005-531709